I have been working out for some time now, mainly running and lifting and I believe that there is a possibility I am training at a rate too fast. My heart rate to be specific. I have been told that my target heart rate for a 21 year old should be around 139-140 beats per min. I have been told by a doctor in the past if I run too fast and my heart rate goes above 150 bpm the body starts to work off sugar instead of fat. Is this true? What should my target heart rate be for a workout? I am considering this as a reason for a lul in my weightloss.

Thanks for any info.

Hi Ann...
I also train quite a bit, running is my thing too. I actually have been wanting to run the NYC marathon, but we'll see. A few years ago I tried using a HeartRate Monitor while I ran or took Spinning class, but I found it confusing and frustrating to always be measuring and looking for my target heart rate. So I gave it up, my husband still uses his to train...I'm not sure if my reply is much help, but when I used the monitor and was in my 'target rate' I typically felt like I was running hard, but could go harder if I had to. Now I try to run the same way....I run about 6 miles a day and try to mix in some intervals and sprints. I try to run the majority of my time in that same place...pretty hard (I'm sweating and pushing, but if I had to I could run much harder).

The only way I think a person could really 'overtrain' is if your entire workout you are going all out...way above your target heart rate and basically just sprinting. Maybe you could actually try to slow just a bit...if you are sprinting and really going all out everday your muscles could retain water, causing a stall. Which heart rate monitor do you use? If it is the same as my husband's I can ask him if his fluctuates over on his target rate. Well, sorry I can't help more. Good Luck!
Jenn

I am 57 years old and I exercise at 150 bpm for hours. If I was burning sugar I would have collapsed long ago.

The formulas used to determine training hear rates are almost worthless. They almost always predict rates much too low.

Just make sure to get enough 'off' time so that your body can recover.

I don't use a heart rate monitor as yet. I am in the market for one but I found out that the monitor that was cheapest and simplest is sold out, and they won't be manufacturing more. I am just really puzzled about this stall, I'm a smart eater and I love my exercise but I am a bit confused. So, thanks for the help, I guess I'll try slowing a bit every once in a while. I don't sprint except for random spurts and I can tell the difference in my muscles the next day.

Thanks again.

don't worry about it - run as hard as you can for as long as you can if you want to burn the most calories, including calories from fat.
For example: 180 lb person running for 30 mins burns 346 kcal at 5 mph; 713 at 10 mph. (kcal estimates from the link in doreen's thread about calorie burning)
if 90% of that 346 was from fat it would be 311 kcal of fat burned.
if only 50% of that 713 was from fat it would be 356 kcal of fat burned.
and I suspect the pct for 10 mph would be more like 70% not 50%.
on the absurd end of the spectrum: you burn virtually 100% of your calories from fat when sitting quietly - but who would suggest that as an exercise option.